Used in army, and more commonly in the polive forces 13-69 is intended to sound, to a civilian, like technical jargon from police/army codes. 13-69 is actually a low-blow insult meaning unlucky cock-sucker. 13 being unlucky, and 69 being an obvious sexual posion. 69

"aw man, my wifekicked me out last night, can i stay at your place?"
"No way! it ain't my fault you're a 13-69"